Flicker control

ABSTRACT

An example system includes a varying resistive device, a controllable resistive device, a power supply to power the varying resistive device and the controllable resistive device, and a controller to control operation of the varying resistive device and the controllable resistive device. The varying resistive device changes a power level used during operation. The controller includes a flicker control portion, wherein the flicker control portion is to control a power level at the controllable resistive device based on changes in the power level used by the varying resistive device to maintain a flicker level below a predetermined flicker threshold.

BACKGROUND

Various system, such as imaging devices are powered by plugging thesystem into an external power supply, such as by plugging into a walloutlet. Such systems may include various subsystems that are powered bythe external power supply at different power levels. For example, aprinter or other imaging system may have a printing engine subsystem, amedia conditioning subsystem, and a finishing accessory subsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of various examples, reference is nowmade to the following description taken in connection with theaccompanying drawings in which:

FIG. 1 provides a schematic illustration of an example system;

FIG. 2 provides a schematic illustration of another example system;

FIG. 3 illustrates a circuit diagram of an example system;

FIG. 4 is a flow chart illustrating an example method for flickercontrol; and

FIG. 5 illustrates a block diagram of an example system with acomputer-readable storage medium including instructions executable by aprocessor for flicker control.

DETAILED DESCRIPTION

Various examples provide for mitigation of flicker that may be caused bya device or subsystem with, for example, frequent cycling between an onor off position or otherwise changing of power level used by the deviceor subsystem. For example, in an imaging system, a heated pressureroller (HPR) may use a heating lamp, such as a tungsten halogen lamp, togenerate heat for the HPR. Due to tight tolerances for the temperatureof the HPR, the heating lamp may be cycled between on and offfrequently. The cycling of the heating lamp may cause a flickering, forexample, in the lights of a building in which the imaging system ishoused. In various examples, a second device or subsystem may be used asa ballast to reduce fluctuations in the power used. For example, in theimaging system using the HPR, an AC-powered dryer may be used in theprint engine. In various examples, the dryer may be used as a ballastsince the dryer may have greater tolerances. In one example, the dryeruses a nichrome wire heating element that has a longer thermal timeconstant than the HPR heating lamp. Thus, flicker may be mitigated ormaintained below a predetermined threshold.

Referring now to the figures, FIG. 1 provides a schematic illustrationof an example system 100. In various examples, the example system 100 ofFIG. 1 may be an imaging system such as a printer, copier, scanner or amulti-function device. The example system 100 illustrated in FIG. 1includes a varying resistive device 110. In some examples, the varyingresistive device 110 changes a power level during operation of thevarying resistive device 110. For example, while being operated, thevarying resistive device 110 may alternate between an on state and anoff state or change between low, medium or high level of operation, thususing a varying level of power. In the example in which the examplesystem 100 is an imaging device, the varying resistive device 110 maybe, for example, a heating lamp for a heated pressure roller (HPR) ofthe imaging system. In this regard, the level of power to the heatinglamp may be changed to maintain the temperature of the HPR within apredetermined range. As described in greater detail below, a varyingresistive device 110, such as a heating lamp, may be a short thermaltime constant heating device.

The example system 100 of FIG. 1 further includes a controllableresistive device 120. As described below, a power level to thecontrollable resistive device 120 may be varied based on changes to thepower level of the varying resistive device 110. In the example in whichthe example system 100 is an imaging device, the controllable resistivedevice 120 may be, for example, a dryer of the imaging system. Asdescribed in greater detail below, a controllable resistive device 110,such as a dryer, may be a long thermal time constant heating device.

The example system 100 of FIG. 1 is provided with a power supply 130 topower the varying resistive device 110 and the controllable resistivedevice 120. In various examples, the power supply 130 may include or becoupled to an AC power source. For example, the power supply 130 mayinclude an AC cord to plug into a wall outlet of a building.

Operation of various components of the example system 100 of FIG. 1,such as the varying resistive device 110 and the controllable resistivedevice 120, may be controlled by a controller 140. In various examples,the controller 140 may be implemented as hardware, software, firmware ora combination thereof. The controller 140 may be a central processingunit (CPU) of the system 100, for example.

In the example system 100 of FIG. 1, the controller 140 includes aflicker control portion 150. The flicker control portion 150 controlsthe power level at the controllable resistive device 120 based onchanges in the power level used by the varying resistive device 110 tomaintain a flicker level below a predetermined flicker threshold. Forexample, the flicker control portion 150 may include logic to calculatea flicker level based on changes to the power level of the varyingresistive device 110. As described above, frequent changes to the powerlevel may cause lights in a building housing the system 100 to flickerat a level that may be perceptible to humans. In one example, if theflicker control portion 150 determines that the flicker level due tochanges in the power level of the varying resistive device 110 isunacceptable (e.g., above a predetermined threshold), the flickercontrol portion 150 may cause the controllable resistive device tooperate at a different power level to mitigate the flickering.

Referring now to FIG. 2, a schematic illustration of another examplesystem 200 is provided. In various examples, the example system 200includes an auxiliary module 210 that may be coupled to a primary device250. In one example, the auxiliary module 210 is a conditioner that canbe coupled to an imaging device, such as a printer. In various examples,a conditioner for an imaging device may be a system which changescertain properties of the print media, for example.

In the example system 200 of FIG. 2, the example auxiliary module 210includes a power supply 220 that may be coupled to an external powersource. In various examples, the power supply 220 includes analternating current (AC) power cord, and the external power source maybe an electrical outlet into which the AC power cord may be plugged.

The auxiliary module 210 includes a power controller 230 coupled to thepower supply 220. In various examples, the power controller 230 includescircuitry to provide power from the external power source, through thepower supply 220, to at least one subsystem, such as the varyingresistive subsystem 240. In one example, the auxiliary module 210 is aconditioner for an imaging device, and the varying resistive subsystem240 may include heat lamps for a heated pressure roller (HPR). Thus, thepower controller 230 can provide power from the external source, such asa wall outlet, through the power supply 220 to the varying resistivesubsystem 240.

Further, as indicated in the example of FIG. 2, the varying resistivesubsystem 240 is to receive control signals from the primary device 250to which the example auxiliary module 210 is coupled. In this regard,the varying resistive subsystem 240 of the example auxiliary module 210may operate, at least in part, based on control signals from the primarydevice 250. For example, the lamps of the heated pressure roller mayoperate under the control of the imaging device to which the auxiliarymodule 210 (e.g., a conditioner) is coupled.

As noted above, in the example system 200, the example auxiliary module210 is coupled to the primary device 250. The primary device 250 may bean imaging system, such as a printer, copier, fax machine,multi-function device or the like. The example primary device 250 ofFIG. 2 includes a power module 260 to receive power from an externalsource. In this regard, an external source for the power module 260 is apower source that is external to the primary device 250. In the examplesystem 200 of FIG. 2, the power module 260 is coupled to the powercontroller 230 of the example auxiliary module 210. In this regard, thepower module 260 receives power, or power signals, from or through thepower controller 230 of the example auxiliary module 210. For example,the power module 260 of the primary device 250 may include an AC plug,and the power controller 230 of the example auxiliary module 210 mayinclude an AC outlet to receive the AC plug of the primary device 250.

The primary device 250 of FIG. 2 further includes a controller 270. Thecontroller 270 provides control signals to at least one subsystem of theprimary device 250, such as the controllable resistive subsystem 280shown in FIG. 2. As noted above, in some examples, the primary device250 is an imaging system. In such examples, the controllable resistivesubsystem 280 may be a dryer subsystem for the imaging device, forexample. The controller 270 may be provided to control operation of thecontrollable resistive subsystem 280 and/or other various subsystemsprovided in the primary device 250. Further, the controllable resistivesubsystem 280 and/or other various subsystems of the primary device 250may operate using power provided from the power module 260 of theprimary device.

Referring now to FIG. 3, a circuit diagram of an example system 300 isillustrated. The example system 300 includes a printer 310 whichincludes a printer controller 312. The printer controller 312 controlsoperation of the printer 310, including various subsystems of theprinter 310, as well as operation of any auxiliary or accessory devicescoupled to the printer 310. In the example system 300 of FIG. 3, theprinter 310 includes a dryer subsystem 314 and a printbar subsystem 316.

The printer 310 of the example system 300 further includes a powersystem 318. In the example system 300 of FIG. 3, the power system 318 ofthe printer 310 includes a 33-volt power supply which is coupled to apower source that is external to the printer 310. The power system 318controls distribution of power to the various subsystems of the printer310. As illustrated in the example of FIG. 3, the 33-volt power supplymay provide AC power to the dryer subsystem 314 and DC power to theprintbar subsystem 316. The power system 318 of the printer 310 iscoupled to an external power source through an interface, such as an ACpower cord 320.

As noted above, the printer controller 312 controls operation of thevarious subsystems. In this regard, in the example system 300 of FIG. 3,the printer controller 312 may transmit signals S2, S3 to the dryersubsystem 314 and signals S6, S7 to the printbar subsystem 316.

The example system 300 further includes an auxiliary module in the formof a conditioner 340 coupled to the printer 310. In some examples, theconditioner 340 may be positioned above a print engine of an imagingdevice, such as the printer 310, for example. The conditioner may becoupled to an external power source through, for example, an AC powercord 342. In various examples, the AC power cord 342 of the conditioner340 may be plugged into a wall outlet (not shown) or other externalpower source for AC power. In one example, the external power source isa 15 amp AC power source.

The conditioner 340 of the example system 300 includes circuitry 344 todistribute power from the external power source, through the AC powercord 342, to various subsystems of the conditioner 340. For example, inthe example illustrated in FIG. 3, the circuitry 344 allows distributionof power to a heated power roller (HPR) subsystem which includes HPRlamps 346. In the example system 300 of FIG. 3, the circuitry 344provides a 24-volt power source to power the HPR subsystem and/orvarious other subsystems of the conditioner 340.

The HPR subsystem and/or various other subsystems of the conditioner 340operate under the control of the printer controller 312 of the printer310. In this regard, in the example system 300 of FIG. 3, the printercontroller 312 may transmit signals S4, S5 to the HPR lamps 346 of theHPR subsystem.

The conditioner 340 of the example system 300 of FIG. 3 further includespower monitor circuits 348 to measure various voltages, currents and/orother parameters related to power. As illustrated by the arrow in FIG.3, various measurements from the power monitor circuits 348 aretransmitted from the conditioner 340 to the printer controller 312 ofthe printer 310. In this regard, the printer controller 312 may use thepower information as factors in operation of various subsystems of theprinter 310 and the conditioner 340. For example, the printer controller312 may vary operation to avoid overload of power systems or to reduceflicker.

The example system 300 further includes an accessory device 360, whichmay be a finisher for the printer 310. In one example, the accessorydevice 360 may be a floor-standing device that is separate from theprinter 310 and is connected, for example, via at least one cable (e.g.,USB cable). In the example system 300 of FIG. 3, the accessory device360 receives control signals from the printer controller 312 of theprinter. Power for operation of the accessory device 360 in the examplesystem 300 is provided through the conditioner 340. For example, asillustrated in FIG. 3, power for operation of the accessory device 360is provided through the circuitry 344 of the conditioner via a 24-voltpower supply 350. In the example of FIG. 3, the power is supplied to afinisher, which may represent a 24-volt DC load.

In one example, the HPR lamps 346 are tungsten halogen lamps to generateheat for the HPR. In one example, the HPR lamps 346 include two lamps of600 and 700 watts. The lamps 346 may be used to maintain a tighttemperature tolerance for the HPR. In this regard, the lamps 346 may becycled on and off. The HPR may have a relatively short thermal timeconstant. Accordingly, the cycle time for the lamps 346 may be short,such as less than one second, for example. The short cycle time maycause flicker in the lights in the electrical system outside the system400.

In various examples, the dryer 314 may be used as ballast to reduce theflicker. In one example, the dryer 314 uses a nichrome wire heatingelement inside an enclosure. In this regard, the dryer 314 may have arelatively long thermal time constant. In one example, the dryer 314includes two dryers that may operate at a maximum power of 500 wattseach. The dryer may operate at 50 Hz AC and may use half-cycle controlto control the temperature of the dryer. Thus, the dryer 314 may beoperated with 100 opportunities each second during which power may besupplied or withheld from the dryer 314. In order to reduce flicker, theduty cycle of the dryer 314 may be adjusted based on changes to thepower level of the HPR lamps to mitigate flicker. In this regard, thedryer 314 serves as ballast, and no power is wasted.

Referring now to FIG. 4, a flow chart illustrates an example method forflicker control. The example method 400 may be implemented in acontroller, such as the controller 312 of the printer 310 describedabove with reference to FIG. 3. In the example method 400 of FIG. 4,received determination is made as to whether a short thermal constantdevice is to receive power in a current power cycle (block 410). Forexample, with reference to FIG. 3, the printer controller 312 maydetermine whether the HPR lamps 346 are to receive power in the currentpower cycle. In this regard, the current power cycle may be eachhalf-cycle of the AC power supply. Further, the determination may bebased on a temperature measurement of the HPR. As in the examplesdescribed above, the short thermal constant device is coupled to thesame power supply as a large thermal time constant device. For example,in the example of FIG. 3, the power system 344 is coupled to the HPRlamps 346 (short thermal time constant device) and the dryer 314 (largethermal time constant device). In the example method 400 of FIG. 4, ifthe determination at block 410 is made that the short thermal timeconstant device is to receive power, power is directed to the shortthermal constant device, and no power is directed to the long thermalconstant device (block 420). Further, if the determination at block 410is made that the short thermal time constant device is to not receivepower, power is directed to the long thermal constant device, and nopower is directed to the short thermal constant device (block 420). Inthis manner, a smooth power load may be maintained to avoid or mitigateflicker events.

Referring now to FIG. 5, a block diagram of an example system isillustrated with a non-transitory computer-readable storage mediumincluding instructions executable by a processor for flicker control.The system 500 includes a processor 510 and a non-transitorycomputer-readable storage medium 520. The computer-readable storagemedium 520 includes example instructions 521-523 executable by theprocessor 510 to perform various functionalities described herein. Invarious examples, the non-transitory computer-readable storage medium520 may be any of a variety of storage devices including, but notlimited to, a random access memory (RAM) a dynamic RAM (DRAM), staticRAM (SRAM), flash memory, read-only memory (ROM), programmable ROM(PROM), electrically erasable PROM (EEPROM), or the like. In variousexamples, the processor 510 may be a general purpose processor, specialpurpose logic, or the like.

The example instructions include adjust a power level for a varyingresistive device based on operating threshold of the varying resistivedevice instructions 521. For example, as noted above with reference toFIG. 3, the operating power level of the HPR lamps 346 may be adjustedto maintain the temperature of the HPR within tight tolerances (orthresholds). The example instructions further include determine a powerlevel change for a controllable resistive device based on adjustment ofthe power level for the varying resistive device and a flicker thresholdinstructions 522. As noted with reference to the example of FIGS. 3 and4, the printer controller 312 may calculate a new power level for thedryer 314 based on the power level change of the HPR lamp 346 and apredetermined flicker threshold. The example instruction further includechange duty cycle of the controllable resistive device to correspond tothe power level change for the controllable resistive deviceinstructions 523. With reference to the example of FIG. 3, the printercontroller 312 may change the duty cycle of the dryer 314 to change thepower level of the dryer 314.

Thus, various examples described herein can mitigate flicker cause byfrequent power level changes of one subsystem. Using a second subsystemas a ballast allows mitigating of the flicker without waste of power.

Software implementations of various examples can be accomplished withstandard programming techniques with rule-based logic and other logic toaccomplish various database searching steps or processes, correlationsteps or processes, comparison steps or processes and decision steps orprocesses.

The foregoing description of various examples has been presented forpurposes of illustration and description. The foregoing description isnot intended to be exhaustive or limiting to the examples disclosed, andmodifications and variations are possible in light of the aboveteachings or may be acquired from practice of various examples. Theexamples discussed herein were chosen and described in order to explainthe principles and the nature of various examples of the presentdisclosure and its practical application to enable one skilled in theart to utilize the present disclosure in various examples and withvarious modifications as are suited to the particular use contemplated.The features of the examples described herein may be combined in allpossible combinations of methods, apparatus, modules, systems, andcomputer program products.

It is also noted herein that while the above describes examples, thesedescriptions should not be viewed in a limiting sense. Rather, there areseveral variations and modifications which may be made without departingfrom the scope as defined in the appended claims.

What is claimed is:
 1. A system, comprising: a varying resistive device,wherein the varying resistive device changes a power level used duringoperation; a controllable resistive device; a power supply to power thevarying resistive device and the controllable resistive device; and acontroller to control operation of the varying resistive device and thecontrollable resistive device, the controller including a flickercontrol portion, wherein the flicker control portion is to control apower level at the controllable resistive device based on changes in thepower level used by the varying resistive device to maintain a flickerlevel below a predetermined flicker threshold.
 2. The system of claim 1,wherein the flicker control portion is to change a duty cycle of thecontrollable resistive device to maintain the flicker level below thepredetermined flicker threshold.
 3. The system of claim 1, wherein thevarying resistive device is a heating lamp for a heated pressure rollerof an imaging system.
 4. The system of claim 3, wherein the heating lampis a tungsten halogen lamp to generate heat from the heated pressureroller.
 5. The system of claim 3, wherein the power level for thevariable resistive device is changed to maintain a temperature of theheated pressure roller within predetermined range.
 6. The system ofclaim 3, wherein the controllable resistive device is a dryer for theimaging device.
 7. A method, comprising: determining whether a shortthermal time constant device is to receive power in a current powercycle, wherein the short thermal time constant device is coupled to acommon power supply with a long thermal time constant device; if theshort thermal time constant device is determined to receive power in thecurrent power cycle, providing power to the short thermal time constantdevice and no power to the long thermal time constant device; and if theshort thermal time constant device is determined to not receive power inthe current power cycle, providing power to the long thermal timeconstant device and no power to the short thermal time constant device.8. The method of claim 7, wherein the determining whether the shortthermal time constant device is to receive powered includes receiving atemperature measurement associated with the short thermal time constantdevice.
 9. The method of claim 7, wherein the short thermal timeconstant device is a heating lamp for a heated pressure roller of animaging system.
 10. The method of claim 9, wherein the heating lamp is atungsten halogen lamp to generate heat from the heated pressure roller.11. The method of claim 9, wherein the long thermal time constant deviceis a dryer for the imaging device.
 12. A non-transitorycomputer-readable storage medium encoded with instructions executable bya processor of a computing system, the computer-readable storage mediumcomprising instructions to: adjust a power level for a varying resistivedevice based on operating threshold of the varying resistive device;determine a power level change for a controllable resistive device basedon adjustment of the power level for the varying resistive device and aflicker threshold; and change duty cycle of the controllable resistivedevice to correspond to the power level change for the controllableresistive device.
 13. The non-transitory computer-readable storagemedium of claim 12, wherein the varying resistive device is a heatinglamp for a heated pressure roller of an imaging system.
 14. Thenon-transitory computer-readable storage medium of claim 13, wherein theheating lamp is a tungsten halogen lamp to generate heat from the heatedpressure roller.
 15. The non-transitory computer-readable storage mediumof claim 13, wherein the controllable resistive device is a dryer forthe imaging device.